1. Field of the Invention
The present invention generally relates to a steer by wire system. More specifically, the invention relates to an end stop and curb feel feature for a steer by wire system.
2. Description of Related Art
In a conventional steering system, the steering wheel is mechanically connected to the steering shaft. When the mechanical end of travel of the road wheel is reached, the steering wheel cannot be rotated any further due to high mechanical resistance. However, a steer by wire system in normal operation has no mechanical coupling to the road wheel. Therefore, when the end of travel condition is encountered, the driver can continue turning the steering wheel. The lack of feedback force is unfamiliar and may be uncomfortable for some drivers. In addition, extensive use of the steering system in an end of travel condition can cause additional wear to the vehicle.
Also related to steer by wire systems, a mechanical connection is provided as a backup steering technique in the event of a steer by wire system failure. The mechanical steering backup may include an electrically released clutch. In normal operation mode, the clutch will be disengaged providing for operation in steer by wire mode. However, if a sensor anomaly or system failure occurs, the system power will be shut off and the clutch will be automatically engaged. Engaging the clutch provides a mechanical coupling between the steering wheel and the road wheel thereby reverting the system to a manual mechanical steering mode. The driver would then be able to operate the vehicle in an emergency situation despite the system failure.
In view of the above, it is apparent that there exists a need for a system to provide end of travel feedback to the driver of a vehicle having a steer by wire system.